The present invention relates to a method of and a device for changing throughgoing openings of a concave in an agricultural working machine, in particular a self-propelled combined harvester.
The individual throughgoing openings of the concave separating area are determined by the distance between the beater strips and wires of the concave. The size of the throughgoing openings is decisive for the efficiency of the threshing of different crop types. For different crop types, differently sized throughgoing openings are needed to guarantee an unobjectionable threshing of the grain. Corn grains for example require greater throughgoing openings than wheat grains.
When the throughgoing openings are too great, a higher portion of non-grain components is separated on the concave, which leads to greater contamination of the grains separated on the concave. To the contrary, the throughgoing openings which are too small lead for example to clogging of the throughgoing openings, and therefore of the concave, with greater grains. Thereby the danger of corn breakage increases, so that the not thrashed crop above the concave separating area is blocked by further subsequent crop and in addition reduces contacting by the threshing drum.
German patent document DE 3832996 discloses a device for adjusting the distance between two successive rods on a concave. The rods are components of the concave and determine the throughgoing size for the crop. By adjusting the distance between two successive rods, in the same concave, without reconstruction of the elements, each type of harvest can be sufficiently threshed and separated. This is achieved in that each second rod is supported turnably. Flap elements are stationarily mounted on the rotatable rods. By turning the rods, the flap elements are moved in the corresponding rotary direction and in the space located in front of the movable rods. The turning rod is moved by the movement to the non-turnable rod.
The disadvantage is here the position which the flap elements assume in the turned position. In the lowered condition the flap elements are arranged inclined under the throughgoing openings. In this way the passage of the crop is prevented. The threshing of the crop is limited, since the free space under the separating surface of the concave is partially filled by the flap elements, that finally limits the further feeding of the crop after the threshing. Since the crop can no longer pass without obstacle between the rods, this leads to clogging in connection with grain breakage.